CVE-2026-48691: FastNetMon Community Edition BGP Data Overflow

Summary

The FastNetMon Community Edition software has a bug that can cause it to overflow when handling large BGP data. This can lead to data corruption or crashes. Update to the latest version to fix this issue.

What to do

No fix is available yet. Check with your software vendor for updates.

Affected software

Vendor	Product	Affected versions
pavel-odintsov	fastnetmon	<= 1.2.9 `cpe:2.3:a:pavel-odintsov:fastnetmon:::::community:::*`

Original title

FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes at...

Original description

FastNetMon Community Edition through 1.2.9 contains an integer overflow in the BGP AS_PATH attribute encoder. In src/bgp_protocol.hpp, the IPv4UnicastAnnounce::get_attributes() function computes attribute_length as 'sizeof(bgp_as_path_segment_element_t) + this->as_path_asns.size() * sizeof(uint32_t)' and stores it in a uint8_t field (line 600-605). Since uint8_t can only hold values 0-255, an AS_PATH containing more than 63 ASNs (2 + 64*4 = 258 > 255) causes silent truncation. The truncated length is used for buffer sizing, while the actual data written is the full untruncated amount, resulting in a heap buffer overflow. Similarly, the path_segment_length field at line 621 is also uint8_t, truncating with more than 255 ASNs.

Vulnerability type

CWE-190 Integer Overflow

CWE-122 Heap-based Buffer Overflow